The present invention relates to separators for storage batteries, and more particularly to separators for sealed lead-acid storage batteries.
Various kinds of separators for storage batteries made of glass fibers have been proposed, for example, as shown in U.S. Pat. Nos. 3,085,126 and 3,862,861. However, such separators have been inadequate for use in storage batteries, particularly sealed lead-acid storage batteries. For example, the separator disclosed in U.S. Pat. No. 3,085,126 has pore diameters so large as to invite a short-circuit between the negative and positive plates and the amount of binder used is so excessive as to contaminate the negative plate. Further, the separator disclosed in U.S. Pat. No. 3,862,861 is so low in mechanical strength that special precautions are needed when handling it. It should be noted that in a sealed lead-acid storage battery, an electrolyte in an amount which is not so excessive as to be fluid must be retained in the micropores of a glass fiber separator, otherwise, due to oxygen and hydrogen gases being generated at the end of the charging operation for the storage battery, the electrolyte will leak out and elevate the concentration in the cells. As a result, the performance and the service life of the storage battery will be impaired. Therefore, separators for storage batteries are needed which can not only absorb very high amounts of electrolyte, but which will have high electrolyte retention, and which will have many micropores of a small diameter. Furthermore, it is important that the separator be easy to handle for ease in assembling the storage battery. Therefore, it must be comparatively high in mechanical strength. Finally, separators for storage batteries should be advantageously made of cheap materials.
The present invention is directed to a separator which satisfies these various requirements.
Thus, a first object of the present invention is to provide a separator for storage batteries which has favorable performance characteristics and a long service life.
A second object of the present invention is to provide a separator for storage batteries which has a very high electrolyte retention, and which has many micropores of a small diameter.
A third object of the present invention is to provide a separator for storage batteries which has a high mechanical strength, which is easy to handle during assembling of the storage battery, and is cheap to produce.
A fourth object of the present invention is to provide a separator for storage batteries which does not contaminate the negative plate and can considerably prolong the life of the storage batteries in which they are used.